Motor vehicles are frequently equipped with active occupant restraint systems such as seat belt assemblies. Seat belt assemblies typically have lap and shoulder belt portions for restraining the occupant in the event of an impact or rollover event. To enhance the comfort and convenience provided by the seat belt system and to provide other functions, retractors are provided which allow the belt webbing to be freely paid-out and retracted when the vehicle is not subjected to unusual acceleration forces or inclination. In the event of exposure to such forces, a retractor control system activates to lock the retractor to prevent additional pay-out (extraction or protraction) of webbing. Thus, the retractor locks in a manner to enable the seat belt webbing to restrain the occupant. Such retractor control systems take various forms. One category of such control systems is known as vehicle sensitive inertial locking systems. These systems are sensitive to acceleration forces acting on the vehicle resulting from a frontal impact, side impact, rollover, and when certain other forces act on the vehicle.
Another category of such retractor control systems is known as belt sensitive control systems. These devices operate much in the manner of a centrifugal clutch and sense the rotational speed of the retractor spool, such that when high angular accelerations of the retractor spool occurs associated with rapid extraction of webbing, the control system engages to lock the retractor. This invention is related to an improved vehicle sensitive retractor inertial locking sensor.
As mentioned previously, vehicle sensitive retractor inertial locking sensors must respond to acceleration loads acting in various axes and planes. Primarily important are impacts to the vehicle creating acceleration loads acting in the horizontal plane, such as front, rear, or side impact conditions. However, if a rollover event has occurred, it is important that the retractor lock to restrain the occupant. Typical inertial retractor locking sensors utilize a pendulum, standing man, or rolling ball type inertial mass to activate a locking lever which engages directly or indirectly with a ratchet wheel of the retractor webbing spool which acts as a spool lock. In response to accelerations of the vehicle, the inertial mass moves to urge the locking lever to engage with the ratchet wheel, thus locking the spool from allowing further extraction of webbing. These devices have been utilized for many decades and have proven to be reliable and effective retractor control systems.
In the operating environment of a passenger car, interior components are subjected to exposure to foreign material such as liquids, dirt, and particles associated with normal or expected use of the vehicle by its occupants. The presence of foreign objects infiltrating into a seat belt retractor mechanism can interfere with operation of an inertia sensitive sensor. Traditional inertial sensors using a rolling ball or standing man type inertial mass can operate improperly in the event that debris remains in contact with the inertial mass or the related components which can interfere with desired lock-up operation of the system. For example, in the case of a rolling ball type mass, foreign particles collecting on the ball mass can become interposed between the ball mass and the associated ball seat, or between the ball mass and the associated actuating lever which senses movement of the ball. The presence of such contaminants can interfere with the designed system tolerances and interaction between actuation components. Moreover, due to the typical manner of providing a sensing lever acted on by a ball mass, very small sized contaminants can produce significant movement of the lever which can lead to inadvertent lock-up behavior. The precision requirements of present designs impose manufacturing cost penalties and capacity constraints.
In one prior art design of a ball mass type inertial sensor, the actuation lever forms a ring which contacts the ball mass along a ring contact line on an upper surface of the ball. As soon as the ball mass starts to move in any direction, the lever begins to lift due to contact with the ring feature. Even normal lever-to-housing parts tolerance variations may cause the lever to begin to lift (from a desired nominal position) and reduce the gap with the associated ratchet wheel, perhaps leading to inducing lockup when the system is not affected by movement/acceleration. This condition leads to an unintentionally sensitive retractor assembly.
Another important consideration in the design and manufacture of automotive components is their tendency to contribute to unwanted noise during vehicle operation referred to generally as buzz, squeak, and rattle (BSR). Existing vehicle sensitive inertia sensors have tendencies to create undesirable noise as the inertial mass moves within its seat and against the associated locking lever and other components.
In view of the above, there is a desire in the design of retractor inertial actuators to improve their tolerance to contaminants and further to provide means for eliminating contaminants which can lead to the above-described improper operation. In addition, there is a need to provide retractor inertial actuators which reduce BSR problems.